Conventionally, there is known a plasma processing apparatus for performing a plasma etching process on a target object by using a plasma. In the plasma processing apparatus, a plasma is generated in a processing chamber by applying a high frequency for plasma generation to an electrode provided in the processing chamber and serving as a mounting table on which a target object is mounted. The plasma etching process is performed on a surface of the target object by ions or radicals in the plasma.
However, in the plasma processing apparatus, a distortion component may be given to the high frequency for plasma generation on a path for transmitting the high frequency for plasma generation to the electrode. For example, a distortion component referred to as harmonic distortion is generated at a frequency that is an integral multiple of a frequency of the high frequency for plasma generation due to non-linear characteristics or minute impedance changes in elements such as a cable for connecting the electrode and the high frequency power source for generating a high frequency for plasma generation, and the like. When the harmonic distortion occurs, distortion of a waveform of the high frequency for plasma generation which is applied to the electrode (hereinafter, referred to as “waveform distortion”) occurs. The uniformity of the plasma deteriorates due to the waveform distortion of the high frequency. Therefore, the uniformity of an etching rate of the target object deteriorates.
There is known a conventional technique for removing harmonic distortion by applying a specific impedance of an impedance element provided on a path for transmitting a high frequency for plasma generation to the electrode to thereby suppress the waveform distortion of the high frequency (see, e.g., Japanese Patent Application Publication No. 2005-203444 and Japanese Patent Application Publication No. H10-241895).
In the conventional technique using an impedance element, it is possible to suppress deterioration of the uniformity of the etching rate which is caused by the waveform distortion of the high frequency applied to the electrode, whereas it is difficult to reduce a difference in the etching rate between plasma processing apparatuses.
In other words, a state of the path on which the impedance element is provided (e.g., a state of a cable connecting an electrode and a high frequency power supply for generating a high frequency for plasma generation or the like) varies depending on plasma processing apparatuses, so that a magnitude of harmonic distortion occurring on the path varies depending on the plasma processing apparatuses. When the magnitude of the harmonic distortion varies depending on the plasma processing apparatuses, it is difficult to sufficiently remove the harmonic distortion by using an impedance element because an impedance of the impedance element is fixed, and large harmonic distortion may remain depending on the plasma processing apparatuses. Accordingly, in case that the impedance element is simply used, the magnitudes of the remaining harmonic distortion become different between the plasma processing apparatuses. Therefore, the magnitude of the waveform distortion of the high frequency applied to the electrode also varies depending on plasma processing apparatuses. The difference in the waveform distortion between plasma processing apparatuses causes a difference in plasma uniformity between plasma processing apparatuses. As a result, the difference in the etching rate between plasma processing apparatuses is increased.